Gauge Cluster Teardown and Rebuild - Beware, Pic Heavy!

Green79Scottsdale · Jun 30, 2016

Tach cluster is finally in and working! Here are some highlights.

Pic #1 - First I hooked up the tach to verify it works. I had no reason to believe it didn't after sending it off to be fixed. Confirmed the rpm's with my SunPro.

Pic #2 - Pulled the dash and the three different bezels to get access to the gas gauge. Had to make sure the old small one I have works. That would suck if it didn't... Good thing it does!

Pic #3 - Pulled the original cluster out. Note: It is very easy to break off the mounting tab on the left side of the housing! Do the squarebody community a service and try to avoid breaking it!

Pic #4 - Transferred the original speedo, voltmeter and coolant temp to the tach housing, along with the small gas gauge and the rebuilt tach. I had previously painted the housing gloss white.

Pic #5 - Just a pic with the black inner bezel installed.

Green79Scottsdale · Jun 30, 2016

Some of my personal thoughts on this whole swap.

If I had to do it over again, I would be open to buying a nice one in good working condition for a couple hundred bucks. This took me a while to actually do, but I was not in any hurry. I could have easily completed it a couple of years ago. I don't know exactly how much $$ I have into it. $25 for the old tach cluster. $55 to get the actual tach fixed. $60 for the correct printed circuit. $30 for the tach wiring harness. Spray paint and new bulbs was probably another $20. Right there is $190! It wasn't "cheap", especially if someone is doing it all at once. Your time is worth something, and I easily spent several hours on the road driving to get stuff.

After studying the electrical schematics for the 1979 trucks, which is like Greek to me, and comparing it to the physical parts I had in front of me, it looked like there was no re-pinning of the cluster plug needed. That's weird, everyone says re-pinning will be necessary. So I took a chance and installed the thing. HAHA!! Everything worked! NO RE-PINNING NEEDED! I will say this with a disclaimer, I will say it is only true for a 1979 truck with a V8 and going from gauges with no tach to gauges with tach. If you are going from idiot gauges to gauges, then yes, re-pinning is necessary, schematics showed that.

So there you go. I can rest easy now that this is DONE! :cheers:

HotRodPC · Jun 30, 2016

So you saved $10 and shipping, maybe $30. BUT, you also got a nicely refurrbed cluster now that is known to work, with a new printed circuit and rebuilt tach so you shouldn't have any problems. You might have gotten one that was wore out and lasted 3 days or been in accurate. I think you did fine.

Green79Scottsdale · Jun 30, 2016

HotRodPC said:
So you saved $10 and shipping, maybe $30. BUT, you also got a nicely refurrbed cluster now that is known to work, with a new printed circuit and rebuilt tach so you shouldn't have any problems. You might have gotten one that was wore out and lasted 3 days or been in accurate. I think you did fine.

You are absolutely right. And I am in no way complaining about the price. For me it was totally worth it. Thank you for putting into words what my brain didn't think of right away.

The best part of this whole was my dad's reaction. For those that don't know, he bought the truck new, and did some upgrades himself over the years. Just stuff like smaller mirror arms, painted the top green from the original white, and put an FM/AM radio in place of the AM. Anyway, I had it at his house the other day and we were out talking by it. So I told him to look inside the truck and see if he can tell what I did to it. He went nuts over it!! I have never seen him gush so genuinely over something automotive! He said it was the coolest things that ever happened to the truck! He likes those upgrades... may not have come on the truck, but it was available at the time. That made it all worth it!

75gmck25 · Apr 7, 2017

A lot of good information about cluster refurbishing. Very useful.

I also replaced the cluster in my '75 with a tach cluster from a '74 sub, which is a direct replacement. The tach works, but is a little flaky sometimes in colder weather.

I did quite a bit of research about this vintage of GM tachs and I found most of my info on Corvette forums. They use a similarly designed tach, but the actual circuit board is shaped differently so you can't use a replacement Corvette board to repair a truck tach.

Bruce

LateOnTheBrakes · Sep 25, 2020

Just to clarify there are a total of 11 bulbs and they are 168, not 194? I got my gauge cluster working this weekend but the backlighting is terrible. I don't want to spend a ton of money on bulbs, especially if it may be the circuit board.

Anyone know a site you can buy 168s in bulk?

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Bextreme04 · Sep 25, 2020

looks like most of your bulbs aren't coming on at all. I'd recommend making sure the contact surfaces on both the bulb holder and printed circuit are super clean and making solid contact. You probably need to bend the tabs on the bulb holders to make sure they make solid contact. I also like to put a dab of DC4 on all the surfaces before assembly to prevent corrosion. Also make sure the contacts on the connector from the cluster to the harness and harness to the ground connections on the parking brake pedal are clean and coated as well. That will make a huge difference in how bright they are.

My78truck · Nov 6, 2020

I am doing the same thing. I want to try and keep mine as stock as possible. I have switched up the incadescent to LEDs. I foimd out the new LED sockets I bought from Super Bright will not click in on the guage cluster so hoping the old ones, after cleaning, will work. Need to take care of some under dash/behind cluster rust abatement/treatment before putting all back.

1979k10 · Nov 6, 2020

^ I used the leds from superbright. Worked great, a little tight to click in but not forced.

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Felipe Acosta · Sep 17, 2021

I am going through the same process. I have ordered the circuit ribbon that goes on the back. Hoping all the gauges work. Thanks for all the info. very helpful the pictures make a huge difference.

Bullet Bob · Dec 15, 2023

Great thread with lots of information I needed since my speedometer needle broke into several pieces and in the process of cleaning up my cluster. Not sure if it’ll work for everyone but I buffed the gauge areas on the clear panel with flitz and it cleared those areas up big time for me.

bowtie queen 72 · Sep 15, 2024

Green79Scottsdale said:
It was at this point that I realized I have a lot of rusty parts, like almost all of them! The metal trim piece especially bugged me, the gauges themselves were more rusty than I realized, the lens was nasty, and I think I ripped the printed circuit beyond use when I was removing some of the light bulbs. I thought I would try to see how clean I could get stuff before I do anything else.

Word of caution!!! The lettering on the gauges do NOT like any type of liquid! Even straight water! I got a paper towel damp, not soaking wet, and started clean the dirt off the tach. HOLY CRAP! I am smearing the paint! Be VERY careful if you need to clean gauges!

Decided to do it right and remove the needles. I had read they can be a pain. You need to go slow. Some said to use a fork. No….. not me. Why use a metal fork when a plastic golf divot repair tool will be easier on the gauge. Slowly work it under the needle and gently start prying. That’s how I did it….

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Another word of caution, if the needles do not want to come loose easily, you might not want to go to far. I was having a tough time with my speedo and broke the shaft the needle gets pressed onto.

It was after breaking the speedo needle that I sat back and evaluated my options. I decided to get a donor cluster for parts. Found one locally for a good price….

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I was looking for basically all the gauges if possible (sans tach), good metal trim piece, and nice rust free clips for the gauges. Got them all.

New vs. old parts…..

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I found this interesting. On clusters with a blank bottom left gauge, it is just a plastic cover over the hole. I did not know that. If you didn’t either, now you do.

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Wedge type bulb, 168 looks to be stock, and socket…

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Here are the differences between a tach cluster housing, and a “regular” gauge housing. Big obvious area is gone for the tach and bulb and gauge clip locations are different. Tach housing on bottom…..

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I

brooksman9 · Friday at 5:10 PM

Can you reach the 5 main bulbs without pulling the cluster? Obviously need to contort a bit.

Turbo4whl · Friday at 5:30 PM

brooksman9 said:
Can you reach the 5 main bulbs without pulling the cluster? Obviously need to contort a bit.

The reason you might not want to change bulbs this way, is it is easy to damage the printed circuit wiring. You can't see it, and it's old.

bucket · Friday at 7:45 PM

Turbo4whl said:
The reason you might not want to change bulbs this way, is it is easy to damage the printed circuit wiring. You can't see it, and it's old.

Very true. Besides that, often the contacts on the printed circuit need cleaned and a bulb replacement may not fix the issue.

Gauge Cluster Teardown and Rebuild - Beware, Pic Heavy!

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